The present invention relates to a pressure control valve for a hydraulic brake system for vehicles comprising a closure member carried by a control piston which has one of its ends guided through an annular seal and in a housing bore, preferably connected to atmosphere, and carried adjacent its other end a support plate for engagement with a valve spring, and a valve seat which is part of an annular body held by a tubular body surrounding the control piston and secured to the housing, the annular body forming between it and the tubular body a return channel incorporating a check valve opening in the direction from the outlet to the inlet chamber, with the annular seal in abutment with a step in the housing and the annular body being in abutment with an inner flange of the tubular body.
A pressure control valve of this type has been disclosed in a copending U.S. patent application of J. Burgdorf, Ser. No. 288,633, filed July 30, 1981, assigned to the same assignee as the present application. The valve disclosed therein affords the advantage of a prefabricated valve unit adapted to be fitted into any type of housing. Because of the small diameter of the sealing elements, the frictional forces acting on the sealing elements are reduced. Further, ease of adjustment is provided by the spring being accessible from the outside.
Also, the overall axial length of this prior art valve is shorter than in other known pressure control valves, such as disclosed in German Patent DE-AS No. 15 80 148, where the valve parts have to be assembled in a bore of the valve housing and the spring is disposed between tha annular seal and the valve seat and has approximately the same diameter as these components.